EP2050536A1 - Verfahren und Vorrichtung zur Feinstbearbeitung eines Werkstücks - Google Patents

Verfahren und Vorrichtung zur Feinstbearbeitung eines Werkstücks Download PDF

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Publication number
EP2050536A1
EP2050536A1 EP08016705A EP08016705A EP2050536A1 EP 2050536 A1 EP2050536 A1 EP 2050536A1 EP 08016705 A EP08016705 A EP 08016705A EP 08016705 A EP08016705 A EP 08016705A EP 2050536 A1 EP2050536 A1 EP 2050536A1
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EP
European Patent Office
Prior art keywords
force
abrasive material
material removal
force profile
workpiece
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08016705A
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English (en)
French (fr)
Inventor
Peter C. Di Nardi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thielenhaus Microfinish Corp
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Thielenhaus Microfinish Corp
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Filing date
Publication date
Application filed by Thielenhaus Microfinish Corp filed Critical Thielenhaus Microfinish Corp
Publication of EP2050536A1 publication Critical patent/EP2050536A1/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B33/00—Honing machines or devices; Accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B35/00—Machines or devices designed for superfinishing surfaces on work, i.e. by means of abrading blocks reciprocating with high frequency

Definitions

  • Microfinishing is a unique process that removes surface defects caused by previous operations to produce a high quality finish.
  • the process involves utilizing an abrasive fed against the workpiece under a low or constant force.
  • the abrasive determines the rate or duration of the feed. After the abrasive removes the initial roughness and reaches the solid, base material, material removal rate is reduced and the abrasive becomes dull. This completes the geometry portion of the microfinishing process, as the abrasive no longer removes a measurable amount of the workpiece material. Continued application of the abrasive to the workpiece functions to create the required surface finish.
  • the microfinishing operation is based on a fixed cycle time of increased duration.
  • the abrasive is fed slowly against the workpiece at a reduced rate to correspondingly reduce or prevent fracturing of the abrasive.
  • While controlling the feed rate to control the force applied to the processing tool can be very effective in achieving a high quality finish it typically requires starting with a low feed rate and a low force or contact pressure between the processing tool and the workpiece to prevent fracturing of the abrasive on the processing tool due to the condition of the workpiece.
  • This process takes into account the worst-case scenario of the surface texture of the workpiece and builds into the microfinishing operation an increased cycle time to address the worst-case scenario. This equates to a fixed cycle time of somewhat longer duration than is necessary, in that a certain amount of time is used in advancing the processing tool slowly against the workpiece to reduce any undesired premature fracturing of the abrasive particles and consequently reducing their useful life.
  • the torque of various servomotors used in the material removal apparatus is monitored and compared to a known predetermined value. If the torque of the servomotors exceeds a predetermined level, the torque is reduced to a level at or below the predetermined level to reduce potential loss of processing tool efficiency.
  • tool spindle and work spindle speeds are adjusted to maintain the predetermined force profile.
  • the tool spindle is arranged to swivel about the center of the workpiece resulting in an oscillation motion which improves the rate of stock removal.
  • Figure 1 is a schematic view of a material removal apparatus according to the present invention.
  • Figure 2 is a top view of a material removal apparatus of the invention, specifically showing the base member along which the oscillation motion takes place;
  • Figure 3 is a stock cycle length/force diagram illustrating the changes in the force profile or curve based on the position along the stock cycle or length in accordance with the present invention
  • Figure 4 is a stock cycle length/force diagram illustrating an alternative embodiment of a force profile or curve according to the present invention.
  • Figure 5 is a stock cycle length/force diagram illustrating a further embodiment of a force profile or curve according to the present invention.
  • FIG. 1 there is shown a microfinishing apparatus, seen generally at 10, for use in finishing a workpiece 12 which could be a ceramic, metal, carbon, graphite, or other material.
  • the microfinishing apparatus 10 includes a tool spindle 14 supporting a processing tool 16 used to finish the workpiece 12. While shown herein as a finishing stone, the processing tool 16 may also include a tape or film having an abrasive material located thereon.
  • a tool spindle servomotor 18 connects to and drives the tool spindle 14 through a pulley and timing belt arrangement 20.
  • the tool spindle 14 is mounted for reciprocal movement on a tool slide 22. As illustrated herein, the tool spindle 14 is mounted on a non-preloaded ball screw 24.
  • a tool slide servomotor 26 connected to the ball screw 24 operates to rotate the ball screw 24 and correspondingly move the tool spindle 14 and processing tool 16 into engagement with the workpiece 12.
  • the tool slide 22 and related pulley and timing belt arrangement 20 is further mounted to a base member 35 to provide a swivel motion to the tool slide 22 through the use of an oscillation servomotor (not shown) so that the complete slide and components may swivel so as to provide an oscillation motion A, along base member 35 with respect to the workpiece 12 as clearly shown in Figure 2 ..
  • the microfinishing apparatus 10 further includes a work spindle 28 including a workpiece support member 30 that supports the workpiece 12 during the microfinishing operation.
  • a work spindle servomotor 32 connects to and drives the work spindle 28 through a drive belt 34.
  • the work spindle 28 operates to move or rotate the workpiece 12 during the microfinishing operation.
  • the tool spindle servomotor 18, tool slide servomotor 26, work spindle servomotor 32 and oscillation servomotor (not shown) are each connected to a servo control mechanism 36.
  • the servo control mechanism 36 connects to a control unit 38.
  • the control unit 38 functions to drive and monitor the parameters of the various servomotors, 18, 26, 32 and the oscillation servomotor (not shown) during the microfinishing operation.
  • a user interface such as a personal computer is used to input specific programming and operation logic into the control unit 38 depending upon the particular requirements for finishing the workpiece 12.
  • a gage assembly 40 including a pair of gage probes 42 is used to monitor the size and shape of the workpiece 12. Input from the gage probes 42 is sent to the control unit 38 that controls operation of the various servomotors 18, 26, 32 and the oscillation servomotor (not shown), in accordance with input feedback received from the gage assembly 40 regarding the size and finish of the workpiece 12.
  • a force measuring device or sensor 44 located on the tool slide 22 measures the contact force applied by the processing tool 16 against the workpiece 12.
  • the force measuring device 44 may be a load cell or other type of measurement mechanism that monitors the force applied on the workpiece 12 by the tool spindle 14.
  • the force applied to the tool spindle 14 correlates to the force applied on the workpiece 12 by the processing tool 16.
  • the present invention monitors and controls the force applied by the processing tool 16 on the workpiece 12 during the microfinishing operation.
  • the processing tool 16 exerts a predetermined and variable pressure or force on the workpiece 12 during the microfinishing operation. Initially, the force on the workpiece 12 is determined from empirical data as different workpieces 12 will require a different initial contact force.
  • the processing tool 16 containing non-renewable abrasives in either a film or tool (stone) format, is positioned against the workpiece 12 at a predetermined force or contact pressure. With the processing tool 16 in contact with the workpiece 12 at the predetermined pressure, the tool spindle 14 drives the processing tool 16 and the work spindle 28 operates to rotate the workpiece 12.
  • the oscillation servomotor (not shown) is also used to swivel the tool slide 22 relative to the base member 35 so as to create an oscillation by the processing tool 16. Since the processing tool 16 is located against the workpiece 12 at start up, if the workpiece 12 has a rough surface texture, it is possible, based upon the contact pressure applied to the processing tool 16 to cause fracturing of the abrasive and thus reduce the overall effectiveness of the processing tool 16.
  • the present invention utilizes the control unit 38 to monitor the amount of starting torque supplied by the tool spindle servomotor 18 to the tool spindle 14 and that supplied by the work spindle servo motor 32 to the work spindle 28 at startup.
  • the control unit 38 compares the starting torque of both the tool spindle servomotor 18 and the work spindle servomotor 32 with pre-established limits. When the starting torque exceeds the predetermined or pre-established limits, the control unit 38 reacts to the high starting torque by sending a signal to the tool slide servomotor 26 to reduce the initial pressure on the processing tool 16. Reducing the initial pressure on the processing tool 16 reduces fracturing of the abrasive on the processing tool 16 when the workpiece 12 has an unexpected coarse or rough surface texture.
  • the starting torque of the work spindle 28 corresponding to the oscillation of the workpiece 12 is also measured.
  • the torque generated by the work spindle servomotor 32 is monitored and compared to predetermined or pre-established limits. In some instances, it may be desirable to reduce the speed of rotation and correspondingly the torque generated by the work spindle 28 rather than reduce the force or contact pressure applied by the processing tool 16 on the workpiece 12. Accordingly, the present invention contemplates controlling the torque generated by the tool spindle servomotor 18 and that generated by the workpiece spindle servomotor 32 so as to enable adjusting the force or contact pressure applied by the processing tool 16 against the workpiece 12.
  • the present invention contemplates reading or obtaining feedback information pertaining to the torque of the tool spindle servomotor 18, comparing it to preset limits and adjusting the torque as necessary, including reducing the force or contact pressure applied by the processing tool 16.
  • the invention also contemplates reading or obtaining feedback information pertaining to the torque of the work spindle servomotor 32 and adjusting the torque of the work spindle servomotor 32.
  • Monitoring and adjusting the torque output of the respective tool spindle servomotor 18 and work spindle servomotor 32 in response to variable workpiece 12 surface textures will reduce potential fracture of the abrasive and help maintain a uniform abrasive life cycle. Reacting to the starting torque in this manner creates a cycle based on incoming surface texture conditions rather than a range of conditions. As opposed to starting with a reduced starting pressure and slowly controlling or increasing the pressure to maintain a desired torque which would increase the overall cycle time.
  • the present invention also contemplates controlling the force or contact pressure on the workpiece 12 during and at the end of the microfinishing cycle or operation.
  • the processing tool 16 is advanced against the workpiece 12 at a constant force or contact pressure by varying the feed rate to maintain the force. Once the initial cutting operation is completed, finishing operation continues until at the end thereof the force on the workpiece 12 is gradually reduced until it reaches zero.
  • One method is to stop the tool slide 22 whereby the processing tool 16 remains stationary, by maintaining the processing tool 16 in a stationary position continued operation of the processing tool 16 will gradually reduce the force or contact pressure.
  • the force or contact pressure applied by the processing tool 16 against the workpiece 12 is controlled throughout and to the end of the microfinishing cycle.
  • the Y-coordinate represents the force or contact pressure applied by the processing tool 16 during the microfinishing operation, with Y I being the initial force, converted to a 0-1 factor, set at the control unit 38 and applied during the microfinishing operation.
  • the X-coordinate also converted to a 0-1 factor, represents the microfinishing cycle length, which can be defined in several ways such as gage distance, time or distance traveled by the tool slide 22.
  • the force (Y) is determined based on the X-coordinate, that is, the force (Y) is the force or contact pressure for a particular X-coordinate.
  • the dotted line 50 in Figure 2 represents a linear force to microfinishing cycle length when the feed rate is gradually slowed. For example, as the feed rate slows, the force (Y) gradually decreases or reduces in a linear manner as illustrated by the dotted line 50. It is desirable, however, to vary the force (y) in a non-linear manner according to various factors such as gage points, time or distance traveled by the tool spindle 14 and correspondingly the processing tool 16.
  • the present invention utilizes a nonlinear force curve or path while maintaining a certain feed profile.
  • the present invention allows for an optimum force profile while maintaining an established feed rate to reduce processing time.
  • the present invention contemplates maintaining the actual force profile by varying the tool spindle 14 speed and the work spindle 28 speed. For example, if the measured force; i.e., the output of the force sensor 44, falls below the optimum force profile or curve, the tool spindle 14 speed can be decreased and the work spindle 28 speed held constant, increased or decreased depending upon the amount of adjustment needed to increase the overall force and bring the measured actual force up to the optimum force profile or curve.
  • the tool spindle 14 speed can be increased and the work spindle 28 speed held constant, increased or decreased depending upon the amount of adjustment needed to decrease the measured force.
  • an increase in tool spindle 14 speed will decrease the force
  • an increase in work spindle 28 speed will increase the force.
  • to decrease the overall actual force it is desirable to increase the tool spindle 14 speed and decrease the work spindle 28 speed.
  • to increase the overall actual force it is desirable to decrease the tool spindle 14 speed and increase the work spindle 28 speed.
  • adjustments to the tool spindle 14 speed and the work spindle 28 speed enable the controller to attempt to follow within limits of the optimum predetermined force profile used in connection with microfinishing a workpiece 12.
  • Figures 4-5 illustrate various force profiles developed based on the selection of the exponent ⁇ .
  • Figure 3 illustrates a force profile using 1 as exponent ⁇
  • Figure 4 illustrates a force profile using for the exponent ⁇ , a value less than 1
  • Figure 5 illustrates a force profile using for the ⁇ exponent a value greater than 1.
  • the X-coordinate can be set based on a variety of factors. For example, using the gage assembly 40 illustrated in Figure 1 , the force profile changes or varies relative to various gage positions. As illustrated in Figure 5 , the force profile reduces from gage point X ultimately to zero as the gage reaches zero, which represents the preset size of the finished workpiece 12. As set forth above, the force profile can be based on time/length of the finishing operation or cycle, or the distance traveled by the processing tool 16.
  • the present invention provides the control unit 38 with the ability to determine a predefined force profile whereby the control unit 38 monitors the force applied to the workpiece 12 throughout the entire process. Because it is the force that is being monitored, the processing time may vary for each part, rather than going through a preset or predetermined finishing cycle based on time or feed amount.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
EP08016705A 2007-10-18 2008-09-23 Verfahren und Vorrichtung zur Feinstbearbeitung eines Werkstücks Withdrawn EP2050536A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US11/975,292 US7645180B2 (en) 2007-10-18 2007-10-18 Method for finishing a workpiece

Publications (1)

Publication Number Publication Date
EP2050536A1 true EP2050536A1 (de) 2009-04-22

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EP08016705A Withdrawn EP2050536A1 (de) 2007-10-18 2008-09-23 Verfahren und Vorrichtung zur Feinstbearbeitung eines Werkstücks

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EP (1) EP2050536A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3006161A1 (de) * 2014-10-09 2016-04-13 Rolls-Royce plc Abrasives verarbeitungsverfahren für turbinenschaufeln

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JP5319798B2 (ja) * 2012-01-25 2013-10-16 ファナック株式会社 入力される電流もしくは電力に応じてトルク指令を制限するモータ制御装置
DE102012207448A1 (de) * 2012-05-04 2013-11-07 Nagel Maschinen- Und Werkzeugfabrik Gmbh Finishverfahren und Finishvorrichtung zur Finishbearbeitung rotationssymmetrischer Werkstückabschnitte
US9180559B2 (en) * 2012-08-16 2015-11-10 Nsk Americas, Inc. Apparatus and method for measuring bearing dimension
CN105051626B (zh) * 2013-03-15 2019-03-15 J·艾伯蒂 力响应动力工具
DE102015217600B4 (de) * 2015-09-15 2020-02-20 Supfina Grieshaber Gmbh & Co. Kg Vorrichtung zur Finishbearbeitung von Werkstücken
CN110340737B (zh) * 2019-06-20 2020-05-22 西安交通大学 基于多轴联动的大离轴量非球面磨削刀具路径规划方法

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US20030154799A1 (en) * 2002-01-17 2003-08-21 Harald Goldau Method for the finishing treatment of workpieces
EP1384553A2 (de) * 1998-12-01 2004-01-28 University College London Poliervorrichtung mit Antriebsvorrichtungen zum Führen des Schleifwerkzeugs entlang einer Präzessionsbahn und Verfahren zu deren Verwendung
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EP1384553A2 (de) * 1998-12-01 2004-01-28 University College London Poliervorrichtung mit Antriebsvorrichtungen zum Führen des Schleifwerkzeugs entlang einer Präzessionsbahn und Verfahren zu deren Verwendung
EP1618991A1 (de) * 2000-05-19 2006-01-25 Applied Materials, Inc. Verfahren und Vorrichtung zur "in-situ" Überwachung der Dicke während des chemisch-mechanischen Planiervorganges
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3006161A1 (de) * 2014-10-09 2016-04-13 Rolls-Royce plc Abrasives verarbeitungsverfahren für turbinenschaufeln
US10287890B2 (en) 2014-10-09 2019-05-14 Rolls-Royce Plc Abrasive processing method

Also Published As

Publication number Publication date
US7645180B2 (en) 2010-01-12
US20090104855A1 (en) 2009-04-23

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